Summary information and primary citation
- PDB-id
-
8q72;
DSSR-derived features in text and
JSON formats
- Class
- DNA binding protein
- Method
- cryo-EM (4.17 Å)
- Summary
- E. coli plasmid-borne jetabcd(e248a) core in a
cleavage-competent state
- Reference
-
Roisne-Hamelin F, Liu HW, Taschner M, Li Y, Gruber S
(2024): "Structural
basis for plasmid restriction by SMC JET nuclease."
Mol.Cell, 84, 883. doi:
10.1016/j.molcel.2024.01.009.
- Abstract
- DNA loop-extruding SMC complexes play crucial roles in
chromosome folding and DNA immunity. Prokaryotic SMC Wadjet
(JET) complexes limit the spread of plasmids through DNA
cleavage, yet the mechanisms for plasmid recognition are
unresolved. We show that artificial DNA circularization
renders linear DNA susceptible to JET nuclease cleavage.
Unlike free DNA, JET cleaves immobilized plasmid DNA at a
specific site, the plasmid-anchoring point, showing that
the anchor hinders DNA extrusion but not DNA cleavage.
Structures of plasmid-bound JetABC reveal two presumably
stalled SMC motor units that are drastically rearranged
from the resting state, together entrapping a U-shaped DNA
segment, which is further converted to kinked V-shaped
cleavage substrate by JetD nuclease binding. Our findings
uncover mechanical bending of residual unextruded DNA as
molecular signature for plasmid recognition and non-self
DNA elimination. We moreover elucidate key elements of SMC
loop extrusion, including the motor direction and the
structure of a DNA-holding state.
